unleash.unleash/docs/sdks/ruby.md

id	title
ruby_sdk	Ruby SDK

    require 'unleash'
  
    @unleash = Unleash::Client.new(
      url: '<API url>',
      app_name: 'simple-test',
      custom_http_headers = {'Authorization': '<Client secret>'},
    )

Read more at github.com/Unleash/unleash-client-ruby